In recent years, various forms of medical treatment and checkups have been performed using an elongated hollow and tubular medical instrument referred to as a catheter. Examples of such medical treatment methods include administering medicine directly into a target lesion by utilizing the elongated property of the catheter, pushing, widening and opening a stenosis region inside a lumen in a living body (e.g., blood vessel) using a catheter equipped with a balloon, which spreads by pressurization, at the distal end of the catheter, a shaving off and opening a target lesion using a catheter equipped with a cutter at the distal portion of the catheter, applying a filler and closing an aneurysm, a bleeding place or a feeding vessel using a catheter. Also, there exists a medical treatment method in which in order to maintain a stenosis region inside a lumen in a living body in an opened state, a tube-shaped stent constituted to be in the shape of net for the side surface thereof is embedded and indwelled inside a lumen in a living body by using a catheter, or the like. Further, there exists a method of sucking a liquid which has become excessive for the internal body, or the like.
In case of carrying out a medical treatment and checkup or the like using a catheter, generally, an introducer sheath is introduced into a sticking region formed in an arm or a leg by using a catheter introducer and a catheter or the like is percutaneously inserted into a diseased region such as a blood vessel or the like through a lumen of the introducer sheath.
The introducer sheath is formed from a sheath tube which is a tubular member provided with a hollow portion through which an elongated body such as a catheter is freely insertable (see Japanese Unexamined PCT Patent Publication No. 2003-510134 and Japanese Unexamined Patent Publication No. 2002-291902). In Japanese Unexamined PCT Patent Publication No. 2003-510134, there is described a configuration of providing a hydrophilic coating on the inner surface of an introducer sheath in order to reduce sliding resistance when inserting an elongated body such as a catheter through the introducer sheath. Also, Japanese Unexamined Patent Publication No. 2002-291902 describes providing a hydrophilic coating on the outer surface of an introducer sheath in order to secure the lubricity of the outer surface of the introducer sheath. Japanese Unexamined Patent Publication No. 2002-291902 also describes an introducer sheath in which the inner diameter at the distal portion thereof is formed to become gradually smaller toward the distal side (see FIG. 4 of Japanese Unexamined Patent Publication No. 2002-291902).
When the inner diameter of the distal portion is formed gradually in smaller size toward the distal side as described in Japanese Unexamined Patent Publication No. 2002-291902 sliding resistance between the inner surface of the distal portion and elongated body such as a catheter becomes large and there occurs a phenomenon that slidability of the catheter or the like is lowered. In order to improve such a situation, it is conceivable, as described in Japanese Unexamined PCT Patent Publication No. 2003-510134, that there is provided a hydrophilic coating on the inner surface of the introducer sheath. However, the heat that is produced at the time of carrying out a shape-application process of the distal portion using a die assembly acts excessively, and there occurs a phenomenon that the hydrophilic coating will peel, will decompose, will degrade or the like. Consequently, the sliding resistance between the inner surface of the distal portion and the elongated body such as a catheter is not lowered substantially and so a difficulty arises in that it is not possible to achieve improvement in the slidability of the catheter or the like.
Also, when pulling out the introducer sheath after being inserted inside the blood vessel in a case in which there is provided a hydrophilic coating on the outer surface of the sheath as described in Japanese Unexamined Patent Publication No. 2002-291902, the hydrophilic coating becomes wet by the blood, lubricity occurs and a situation results in which the friction resistance is small. Consequently, it is possible to pull out the introducer sheath rather smoothly. However, at the beginning of the use of the introducer sheath, the hydrophilic coating is under a dry condition, so that the sliding property is bad and the friction resistance thereof is large. Consequently, when inserting it from the skin toward the inside of the blood vessel, the insertion resistance of the introducer sheath is undesirably large.